Certain bis-2-thiazolidinethiones



United States Patent 3,215,703 CERTAIN BIS-Z-THIAZOLIDINETHIONES Frank A. V. Sullivan, Westfield, and Arthur C. Lindaw,

Somerville, N.J., assignors to American Cyanamid Company, Stamford, Conn., a corporation of Maine N0 Drawing. Filed Feb. 28, 1962, Ser. No. 176,435 4 Claims. (Cl. 260306.7)

The present invention is concerned with a new class of compounds useful in forming vulcanized and vulcanizable polychloroprene compositions.

In general, the novel compounds of the invention may be defined as Z-thiazolidinethiones of the structural formula S-C=S s=o-s (I) wherein R may be an ,alkylene, cyclohexylene or phenylene. Use of these compounds in vulcanizing polychloroprenes forms in part subject matter of our copending application Serial No. 282,856, filed May 24, 1963 as a continuation-in-part.

As used in this discussion, the term polychloroprene includes not only polymers of chloroprene (2-chloro-l,3- butadiene) but also copolymers thereof with polymerizable vinyl or diene compounds wherein chloroprene is the predominant monomer. Commercially these polymers and copolymers are available under a variety of type designations, usually grouped as general-purpose types or specialty types.

General-purpose polychloroprenes or neoprenes also usually are grouped in two classes, the sulfur-modified and the non-sulfur-modified types. Sulfur-modified neoprenes, such as types GN, GN-A and GRT, require only metallic oxides for vulcanization, since they contain sulfur or such sulfur compounds as thiuram disulfide. In contrast, non-sulfur-modified neoprenes, such as types W and WRT, have a more uniform molecular structure and do not contain sulfur, thiuram disulfide or other com pounds capable of decomposing to yield either free sulfur or a vulcanization accelerator. They require not only metallic oxides, but also accelerators to develop proper cures.

Neoprene types W and WRT, for example, are normally formulated with a metallic oxide such as magnesia or zinc oxide. An accelerator still is generally necessary to provide acceptable curing characteristics and vulcanizable properties. Many commercially-available rubber accelerators, such as the thiazoles and the unsubstituted thiazolines, have very little practical value as active accelerators for polychloroprenes such as type W. Others, such as most dithiocarbamates, are too active and have serious scorching tendencies. Among the accelerators useful for other purposes which have been proposed for the purpose include such widely varied materials as:

Diorthotolylguanidine salt of dipyrocatechol borate Ethylene thiourea Tetramethylthiurammonosulfide Salicylic acid Butyraldehyde-aniline condensate Butyraldehyde-rnono butylamine condensate Ethyl chloride, formaldehyde, ammonia reaction product Diphenylguanidine plus sulfur In general, they either do not provide the desired vulcanizate or they are too scorchy. The most generally useful and perhaps most effective has been found to be 2- mercaptoimidazoline (ethylene thiourea). However, it too has not proved wholly satisfactory, its scorch tendencies being too high.,

Surprisingly, compounds of this invention are found excellent as accelerators for polychloroprenes. They give safe processing of neoprene types W and WRT. They have a markedly delayed action and therefore do not cause premature vulcanization or scorching. Physical properties of resultant vulcanizates are comparable to those obtained by the use of ethylene thiourea. The scorching time is considerably extended over that provided by ethylene thiourea.

Accelerators of this invention may be prepared by several different general procedures. In the first, carbon disulfide is reacted directly with an N-substituted betaaminoethanol, presumably according to the reaction on \I a S C s CH2-S In the second method, a modification of the first, carbon disulfide is first reacted with aqueous potassium hydroxide and ethanol, and the resulting xanthate is reacted with an N-substituted beta-aminoethanol, presumably according to the reaction H5620 OH2NH C=S CHzOH CHr-N C=S KOH CzH5OH CH2S In a third method, ethylene dibromide is reacted with a diaryl thiourea and the resulting 3-aryl-2-aryliminothiazolidine is then reacted with carbon disulfide.

In accordance with these methods, the following 3- substituted Z-thiazolidinethiones may be prepared and used in the practice of the present invention:

3 -methyl-2-thiazolidinethione 3-ethyl-2-thiazolidinethione 3 b eta-hydroxyethyl -2-thiazolidinethione 3 (b et a-methoxyethyl -2-thi azolidinethione 3 -n-butyl-2-thiazolidinethione 3 -isob utyl-2-thiazolidinethione 3-cyclohexyl-2rthiazolidinethione 3 -benzyl-Z-thiazolidinethione 3 (p-methylbenzyl) 2-thiazolidinethi one 3 (p -methoxybenzyl -2-thiazolidinethione 3- (p-chlorobenzyl -2-thiazolidinethione 3-( 1-naphthylmethyl)-2-thiazolidinethione 3 (beta-phenylethyl) -2-thiazolidinethione 3- Z-furfuryl -2-thiazolidinethione 3 -morpholinomethyl-2-thiazolidinethione 3 -phenyl-2-thiazolidinethione -3-o-tolyl-Z-thiazolidinethione 3-p-tolyl-2-thiazolidinethione 3-(o-methoxyphenyl)-2-thiazolidinethione 3- p-methoxyphenyl -2-thiazolidinethione 3- (p-ethoxyphenyl -2-thiazolidinethione 3 p-chlorophenyl -2-thiazolidinetl1ione 3-alpha-naphthyl-Z-thiazolidinethione 3 ,3 -methylene-bis Z-thiazolidinethione) 1 3 ,3 '-propylene-bis 2-thiazolidinethione) 1 3,3'-butylene-bis (2-thiazolidinethione) 1 3 ,3 -ethylene-bis (Z-thiazolidinethione) 1 1,4-cyclohexylene-bis( 2-thiazolidinethione) 1 1,4-phenylene-bis 2thiazolidinethione) 1 1 These are new compounds.

In practice, the amount of accelerator which may be used with the chloroprene polymer stock may be varied within wide limits, according to the result desired. In general, from about 0.1% to about 1.5% of the accelerator based on the weight of the chloroprene polymer is employed. It is preferred to use from about 0.25% to about 0.65% of the accelerator based on the weight of the chloroprene polymer present in the stock to be vulcanized and in general this will be found to be good practice.

Accelerators of this invention may and will be used in conjunction with conventional compounding ingredients used in the preparation of polychloroprene vulcanizates. Typical examples of such ingredients include antioxidants, metallic oxides, colors, softeners and peptizers, fillers and extenders, reinforcing materials and carbon blacks, and fatty acids and lubricants.

Typical polychloroprenes, such as types W and WRT, usually are compounded by milling together the ingredients. For maximum activitiy of the 3-substituted 2-thiazolidinethiones, it is necessary that the order of addition of the ingredients be that shown in the examples.

The invention will be further described in conjunction with the following illustrative examples. Therein all parts and percentages are by weight unless otherwise noted and all temperatures are in degrees centigrade.

To illustrate the preparation of the compounds of this invention, the following several examples of the preparation of new compounds are given.

EXAMPLE 1 S-(p-methylbenzyl) -2-thiazolidinethz'one Add 30.7 parts of Z-(p-methylbenzylamino)ethanol to 31.5 parts of carbon disulfide with external cooling. The resulting mixture is heated in an autoclave at 140 C. for 4 hours. The colorless, crystalline product obtained by crystallization of the crude product from alcohol melts at about 113 C.

Analysis.Calcd. for C H NS C, 59.3; H, 5.83; N, 6.28; S, 28.7. Found: C, 59.3; H, 5.56; N, 6.34; S, 29.0.

EXAMPLE 2 3- (p-methoxybenzyl) -2-thiazolidinethione Add 42 parts of 2-(p-methoxybenzylamino)ethanol to 44.2 parts of carbon disulfide with external cooling. The resulting mixture is heated in an autoclave at 140 C. for hours. The colorless crystalline product obtained by crystallization of the crude product from alcohol melts at about 104 C.

Calcd. for C H NOS C, 55.2; H, 5.44; N, 5.86; S, 26.8.

Found: C, 55.3; H, 5.36; N, 5.80; S, 27.1.

4 EXAMPLE 3 3-ethyl-2-thiazolidinethione HzCN /o=s HzCS To a solution of 20.3 parts of potassium hydroxide in 133 parts of anhydrous ethyl alcohol, add with stirring 81.5 parts of carbon disulfide. To the resulting yellow slurry, add with stirring and cooling, 89 parts of Z-(ethylamino)ethanol. The resulting mixture is then refluxed for about 16 hours. After removing the solvents by distillation from a steam bath, the insoluble material is removed by filtration. The crude oily product (filtrate) is fractionated by distilling in vacuo, and the portion boiling at approximately 135-136 C. at 1 mm. pressure is collected. The product is a light yellow, viscous oil.

Analysis.-Calcd. for C H NS C, 40.8; H, 6.1; N, 9.5; S, 43.5. Found: C, 41.0; H, 6.18; N, 9.38; S, 43.6.

EXAMPLE 4 3- beta-hydroxyethyl -2-thiaz0lidinethi0ne CHzCHzOH H C-N A mixture of 210 parts of diethanolamine and 304 parts of carbon disulfide is heated in an autoclave at C. for 4 hours. After extracting the product twice'with 250 parts of water, the residue is purified by a vacuum distillation. The product, boiling at 2l3-2l9 C. at a pressure of 7 mm. of mercury, is a light yellow oil.

Analysis.Calcd. for C H NOS C, 36.9; H, 5.5; N, 8.6; S, 39.2. Found: C, 36.4; H, 5.68; N, 8.44; S, 40.7.

EXAMPLE 5 3-(beta-meth0xyethyl)-2-thiaz0lidinethione CHzCH O CH H ON I C=S Hz S A mixture of 21.4 parts of 2-(beta-methoxyethylamino) ethanol and 21.7 parts of carbon disulfide is heated in an autoclave at 140 C. for 4 hours. The reaction mixture is distilled in vacuo. The product is a yellow oil boiling at about ]73-175 C. under a pressure of 3.5 mm. of mercury.

Analysis.-Calcd. for C H NOS C, 40.7; H, 6.2; N, 7.9; S, 36.1. Found: C, 41.9; H, 6.1; N, 8.14; S, 30.1. The intermediate, 2-(beta-methoxyethylamino)ethanol is prepared by reacting the p-toluenesulfonyl ester of betamethoxyethanol with monoethanolamine in the presence of sodium hydroxide at 130 C. The compound boils at 99-103" C. under a pressure of 10 mm. of mercury.

EXAMPLE 6 3-cycl0hexyI-Z-thiazolidinethione CH; CHz (5H.

CH H2GN o=s H2CS/ A mixture of 71.5 parts of 2-(cyclohexylamino)ethanol and 76 parts of carbon disulfide are heated in an autoclave at 138140 C. for 4 hours. After crystallization from ethanol, the colorless crystalline product melts at 120-1205 C.

Analysis.-Calcd. for C H NS C, 53.8; H, 7.4; N, 6.9; S, 31.9. Found: C, 54.1; H, 7.6; N, 7.1; S, 32.4.

EXAMPLE 7 3-(beta-phenylethyl)-2-thiaz0lidinethione EXAMPLE 8 3- (1 -naphthylmethyl )-2-thiaz0lidinethi0ne H2C-S A mixture of 57 parts of carbon disulfide and 41.7 parts of 2-(l-naphthylmethylamino)ethanol is heated in an autoclave at 120 C. for 3 hours. After crystallization from alcohol, the product consists of colorless crystals melting at 121.5-122" C.

Analysis.-Calcd. for C H NS C, 64.8; H, 5.02; N, 5.40; S, 24.7. Found: C, 65.0; H, 4.09; N, 5.53;

EXAMPLE 9 A mixture of 38 parts of carbon disulfide and 31.8

parts of 2-(2-furfurylamino)ethanol is heated in an autoclave for 2 hours at 120 C. The product, after crystallizing from ethanol, consists of colorless crystals melting at 69-70" C.

Analysis.Calcd. for C H NOS C, 48.2; H, 4.52; N, 7.04; S, 32.2. Found: C, 48.0; H, 4.58; N, 6.84; S, 32.7.

EXAMPLE 1O 3,3-ethylenebis(Z-thiazolidinethione) HzC-S A mixture of 148 parts of N',N'-bis (beta-hydroxyethyl) ethylenediamine and 304 parts carbon disulfide is heated in an autoclave at 140 C. for 4 hours. After cooling, the viscous lower layer is separated and is mixed with 800 parts of acetone. The resulting crystalline product is filtered off. After recrystallization from o-dichloro- S-CHz 6 benzene, the product consists of cream-colored needles melting at 253254 C.

Analysis.-Calcd. for C H N S C, 36.4; H, 4.50; N, 10.6; S, 48.5. Found: C, 36.8; H, 4.28; N, 10.0; S, 48.5.

EXAMPLE 11 3-is0bmyI-Z-thiazolidinethione 5 CH;CHCH3 H2C-N /C=S H2CS While cooling, add 45.6 parts of carbon disulfide to 35.0 parts of 2-(isobutylamino)ethanol. The resulting mixture is heated in an autoclave at C. for 3 hours. The crude oily reaction product is stirred with 200 parts of water. The water-insoluble oil is then extracted with ether, and the ether is removed by distillation. By distilling the residue in vacuo, a yellow oil boiling at 178-185" C. at 6-7 mm. of mercury pressure is obtained.

Analysis.Calcd. for C H NS C, 48.0; H, 7.40; N, 8.00. Found: C, 47.5; H, 7.56; N, 7.80.

For purposes of comparison, in addition to the new compounds shown in Examples 1-11, the derivatives of 2-thiazolidinethione shown in Table I were prepared. These compounds have been previously reported in the chemical literature, and in Table I the melting points found are compared with the melting points given in the references.

EXAMPLE 12 In the following illustrative examples of the use of the compounds of this invention, a master batch of polychloroprene (type W) is prepared by placing 600 parts of neoprene W on a two roller mill at 50 C. Thereto in the following order is added 12 parts of phenyl-fi-naphthylamine 12 parts of light-calcined MgO 30 parts of zinc oxide 174 parts of reinforcing black 3 parts of stearic acid and milling is carried out for about fifteen minutes. As noted above, care must be exercised in compounding polymers of this type that the several ingredients are added in the order shown above. If this is not done the desired product properties are not obtained. This master batch is used in the following examples.

EXAMPLE 13 Two samples, each of 400 parts of the master batch of Example 12 are separately placed on a 2-roller mill, the front and back rolls having temperatures of 45 and 75 C., respectively. To the first is added 1.45 parts of 3- benzyl-2-thiazolidinethione over 0.5 minute. To the second an equal amount of 2-mercaptoimidazoline (ethylene thiourea) is added as the accelerator, replacing the 3- benzyl-2-thiazolidinethione. The samples are milled for 23 minutes, conditioned at 73 C. and 61% relative humidity for about 18 hours and then cured at 153 C. for

. "e the first added. Addition of stearic acid or other fatty acid to improve distribution of the carbon black should follow the latter. The following examples illustrate this point.

at which the viscosity of the unvulcanized rubber reached EXAMPLE 1 a value of 5 Mooney units above the minimum, as meas- 0 ured on a Mooney viscometer by ASTM Designation Priipal'atlonpf batches as 111 mp 12 1S repeated D1077 55T, at a temperature f 250 a number of times, on a two roller mill at about 50 C., The tensile properties of the vulcanized rubber, namely adding to Parts Of p y m p yP the modulus or stress, percent elongation and stress relaxasame convefltlonal Fompoundmg lngredfeflts, ldentlfied tion or tension set, are measured by the procedures of as follows, but varylng the Order of addltloll- ASTM Designation D412-51T. The stress relaxation is (A) 12 parts of ihenyl-beta-naphthylamine the increase in length expressed as percent of the original (B) 2 parts f lighp l i d magnesium Oxide length when rubber is stretched and released. an 30 pal-ts f 21110 oxlde The compression set of the vulcanized rubber is meas- (D) 174 parts f i f i black ured by the procedure of ASTM Designation D395-53T (E) 3 parts f stearic acid using a 30% compression for five hours at 100 C. Como pression set is the amount (percent) by which a standard Thelerafter with the 5 roll at about 45 and test piece fails to return to its original thickness after the back roll at about 75 to 400 P Samples of the being subjected to a standard compressive load for a fixed smprepared batches pl mmute period of time parts of 3-benzyl-2-thiazol dinethione and the mix is The results of the tests are shown in Table H as the milled for 23 minutes. It 15 then conditioned at 73 C. average of two runs for each accelfiraton and about 60% relative humidity for about 18 hours TABL I and then cured at 153 C. for twenty minutes. The E I effect of varying the order of addition on the scorch 2 Mercapto 3 Benz 12 time and modulus is illustrated in the following table. imidazoline thiaigli ine- TABLE IV S h, m t 10 26 Order of Addition Modulus 368 Mdu13s ?p.s.i.) 1,450 1,365 30 W 9 Compression Set (percent 41. 8 41. 9 (mum) (PS-L) Stress Relaxation (percent): 1 2 3 4 5 {aer t 3%} 33? 011 EL 1011 Tensile ftren ih at Break (p.s.i.) 3,100 3,160 g g g E Elongation at Break (percent) 505 51a 35 B C D E A 33 880 o D B A E 1 As shown in Table II, polychloroprcne compounded with g g 8 g g 1' 23 3-benzyl-2-thiazolidinethione is superior in scorch re- E A B D C 39 I: 200 sistance and stress relaxation and is equal in tensile 8 g i g; 355 modulus and compression set properties to that com- 40 D C B A E 1 pounded with the commercially-available Z-mercap- E g g g toimidazoline previously considered as the best available agent.

EXAMPLE 14 EXAMPLE 16 l Repeating Example 15, substituting 3-methyl-2-thia- The procedure of Example 13 is followed substitutzolidinethione f the 3 benz 1 com ound h h mg equal amounts of other 3-subst1tuted s-thiazolidinesame efirect of varying the of adgition s Owed t e thiones for the 3-benzyl-2-thiazolidinethione. Illustrative results are shown in Table III. As may be seen there- EXAMPLE 17 from, the Z-thiazolidinethiones of this invention are much Repeating Example 15, using as the accelerator the superior to 2-mercapto1m1dazoline 1n scorch resistance. Z-mercaptoimidazoline used for comparative purposes TABLE III Elon a T 1 Stress Derivative of Z-Thiazolidinethione Scorch, 200% 300% lOD ZIt stfeiin gt li i r i i h t 1n. Modulus, Modulus, Break, at Break, Percent p.s.1. p.s.i. p.s.1. p.s.i. Elong., Percent 3-Methyl 16 800 1, 650 440 10 725 1, 525 510 g: i 0 24 700 1, 475 500 3, 25. 3 34. 5 22 675 1, 400 520 3, 250 23. 0 40. 3 26 500 1, 570 3, 250 20. 3 40. 6 25 600 1, 300 520 a, 100 25. 4 20 650 1, 375 500 a, 050 2-Mercaptolmidazoh 8 625 1, 350 550 3, 325 23. 8 32. 5

Preparation f a master batch comprising the poly in Example 12 as the accelerator showed no substantial ggg 'il s ggwi iggie gr $312336 23 1 3132 51 effect1 on the vulcanized product was produced by changin t e order of dd't' noted that the lngredients were added in a specifically 70 r reason t f th d f designated order. To obtain the delayed action accelers I 18 l o or er 0 a of ator effect with the vulcanization assistants of the present conventlonal q f f Ingredients before addmg the invention, it is necessary that the magnesium oxide, the acc eler ator of .mventlon are not Wholly understood zinc oxide and the carbon black be added in that order. It 18 hlghly 'p g- Nevertheless, it is a precaution If an antioxidant such as the amine is used, it should be 75 that must be observed to obtain optimum results.

9 10 We claim: References Cited by the Examiner 1. A compound Of the formula UNITED STATES PATENTS 2,726,221 12/55 Semegen et a1 26023.7 H20 CH1 5 2,766,223 10/56 Goshorn et a1 260-795 2,784,196 3/57 Bacchetti 260-306.7 2,911,419 11/59 Hughes 260-306] wherein R is selected from the group consisting of alkylene of 14 carbons, phenylene and cyclohexylene. I

2. 3,3'-ethy1ene-bis(Z-thiazolidinethione). N CHOLAS RIZZO Prlmanj Exammer' 3. 3,3'-cyc1oheXy1ene-bis(2-thiazolidinet1hione). 10 LEON BERCOVITZ, Exammer- 4. 3,3'-phenylene-bis(Z-thiazolidinethione). 

1. A COMPOUND OF THE FORMULA 